DE 10 2012 103 581 A1 presents a generic adjustable camshaft having an outer shaft and an inner shaft, and the inner shaft extends through the outer shaft, which is of tubular form, and said inner shaft is rotatable in said outer shaft. By way of a bolt, a cam element which is held rotatably on the outer shaft is connected rotationally conjointly to the inner shaft, such that, in the event of a rotation of the inner shaft relative to the outer shaft, a change in the phase angle of the cam element on the outer shaft is realized.
The cam element which is rotatable on the outer shaft forms, together with a shaft passage in the cam element, a plain bearing arrangement on the outer side of the outer shaft, and the plain bearing arrangement is supplied with lubricant via a gap between the inner shaft and the outer shaft.
The cam element is in contact with a pick-off element to the valve drive, whereby it is often the case that radially asymmetrical forces act on the cam element. This can give rise to tilting of the cam element relative to the longitudinal axis of the camshaft, and to increased loads in the outer regions of the bearing surfaces, which can lead to so-called edge loading. This arises if, in the event of tilting of the cam element on the otherwise cylindrical outer shaft, only the marginal region of the bearing surface, that is to say for example the outer locally limited region in the longitudinal axis direction, of the shaft passage, or the marginal region of the seating point on the outer shaft, accommodates the entirety of the operating forces on the cam element. Finally, such edge loading leads to increased wear and to increased friction between the cam element and the outer shaft, and must therefore be avoided.
DE 100 54 622 A1 has disclosed a valve actuation element, and a rolling-bearing-mounted outer ring is provided which is in contact with the cam contour of a cam element. The outer ring is in a rolling-bearing-mounted configuration by way of an inner ring, and the bearing unit formed by the outer ring and the inner ring is mounted in tiltable fashion on a bearing bolt. For this purpose, the bearing bolt is of spherical form. Owing to the degree of freedom that is obtained for a tilting movement of the outer ring to be performed, said outer ring can be guided against the cam contour of the cam element so as to be in linear contact therewith, without edge loading arising between the cam contour and the pick-off element, that is to say the outer ring. In this case, however, the arrangement of a rolling bearing unit which is mounted in tiltable fashion on a bearing bolt cannot readily be implemented for the mounting of a cam element on an outer shaft of an adjustable camshaft.